1. Field of the Invention
This invention relates to a method of and an arrangement for minimizing power consumption of a battery-operated, wireless reader for electro-optically reading machine-readable indicia such as bar code symbols, and of minimizing latency of data generated by, and transferred from, the reader to a wireless data collection terminal remote from the reader and in wireless communication therewith over a short range network, especially a Bluetooth network in which the reader and the terminal are Bluetooth-compatible devices in compliance with Bluetooth standard, version 1.1.
2. Description of the Prior Art
A reader for electro-optically reading machine-readable indicia such as bar code symbols, both one- and two-dimensional, is well known in the art. In applications requiring portability, the reader is typically held in an operator's hand and aimed at a symbol to be read. A trigger on the reader is manually actuated by the operator to initiate reading. In one type of reader, a light beam is projected from the reader and swept by a scanner across the symbol for reflection therefrom, a detector detects the light reflected from the symbol and generates an electrical signal indicative of the symbol, and signal processing circuitry digitizes and decodes the signal into data related to the symbol. In another type of reader, the field of view of the detector is swept by the scanner. In still another type of reader, an imager, such as a two-dimensional, solid-state, charge coupled device (CCD) array captures an entire image of the symbol, and the image is then processed to obtain the data related to the symbol. In each case, the data is sent to a remote host, for example, a data collection terminal, to access a database for retrieval of information, such as price, in real time.
Again, for reasons of enhancing portability, it is known to eliminate electrical power and data cables between the reader and the host. Thus, a battery, typically rechargeable, is mounted in the hand-held reader, in order to eliminate the power cable. Also, a wireless transceiver is mounted in the reader and the host to transmit the data and receive the retrieved information, in order to eliminate the data cable.
As advantageous as the use of batteries are, experience has shown that they are unsatisfactory in certain applications. Thus, in the case of tracking mail and parcel deliveries, a delivery person typically actuates a hand-held, battery-operated reader to read a bar code symbol on each item to be delivered. Each symbol can be read multiple times, for example, at the pick-up point, at various transfer places en route to a destination, and at the destination, all for the purpose of providing real time tracking of the delivery. The reader has electrical components which consume power and, over the course of a day, for example, a six-hour shift, the battery weakens and discharges. The battery could be recharged, but this requires down-time during which the reader is unusable. A spare battery could be used as a replacement, but this represents still another accessory to be carried and possibly misplaced. A larger battery would not discharge as quickly as a smaller one, but the larger battery adds extra weight and, again, is not a satisfactory answer to the delivery person who wishes to lighten his or her load, particularly if the reader is a wearable device such as a finger-mounted reader.
The use of wireless transceivers has also proven unsatisfactory in certain cases. Thus, the time it takes for data generated by the reader to be delivered to the host, as well as the time it takes for an acknowledgment signal to be received at the reader from the host, should be minimized. This time, also known as data latency, is desired to be as small as possible in order to provide the delivery person with positive feedback as quickly as possible.